Seabrook gate complex, CMAR

New Orleans, Louisiana

Dewatering services needed as a major part of the hurricane protection system designed by the USACE.


Design and oversight of a dewatering system for the construction of a new levee wall system, vertical lift gates, and sector gates within the New Orleans IHNC. The biggest challenge to the project was a scour hole that extended to ±EL-87 caused by a previous bridge pier that crossed Navigation Canal.


Installation of 42 deepwells, unwatering system, rewatering system, and operation and maintenance for project crossing Navigation Canal. Alberici conceptualized several accepted innovations during pre-construction that reduced risks and  project costs during construction, including a temporary rock dike across the canal that reduced tidal flow to allow for use of a cofferdam and design/build dewatering system. The contractor backflled the scour hole with SP Sandy Soils and Griffin jetted deep wells that extended up to 75 ft. deep in the canal section of the project. This allowed for a subgrade of EL -28 to be achieved.


These solutions eliminated the need for the more expensive tremie slab method. These VE concepts saved USACE $16M with a 3-month schedule reduction from the critical path and provided temporary flood protection during construction, allowing USACE to achieve their congressionally-mandated intermediate milestone requirement for 100-year perimeter flood protection. Dewatering was performed with 42 deepwells with unwatering and rewatering pumps. personnel, Griffin achieved the required drawdown and treated for required VOCs and TSS and met the client’s needs.